Wireless communication networks are known. In a cellular system, radio coverage is provided to user equipment, for example, mobile telephones, by geographical area. Those geographical areas of radio coverage are known as cells. A base station is located in each geographical area to provide the required radio coverage. A base station may support more than one cell providing coverage in the same geographical area. User equipment in the area served by a base station receives information and data from a base station and transmits information and data to a base station.
Information and data transmitted by the base station to the user equipment occurs on channels of radio carriers known as downlink carriers. Information and data transmitted by a user equipment to the base station occurs on uplink channels of radio carriers known as uplink carriers.
In known wireless telecommunication networks, user equipment can move between geographical base station coverage areas. Services provided to user equipment are typically overseen by a radio network controller (RNC). The RNC communicates with user equipment via base stations and determines which base station each user equipment is primarily connected to. Furthermore, the RNC acts to control and communicate with a base station and user equipment when user equipment moves from a geographical area served by one base station to a geographical area served by another base station, or between geographical areas served by the same base station.
An area served by any particular base station typically comprises several sectors which together define a coverage area for that base station. Typically, a base station serves three sectors. Those sectors may be served by separate antenna arrays provided on the base station. As well as controlling movement between base station coverage areas, the RNC also has visibility of, and communicates with, the base station and user equipment when the user equipment moves between sectors within a geographical coverage area served by a single base station.
Movement between the sectors provided by a single base station and movement between coverage areas served by different base stations are known as “mobility events” and/or “relocation”, and are overseen by the RNC. Typically, the extent of the involvement of the RNC in such mobility events or relocations will depend upon the radio state of operation of the user equipment. For example, relocation of user equipment when that user equipment is in a highly active state (ie, actively supporting communication of data between user equipment and a source base station in a cell_DCH state) involves an active control of handover by the RNC from a source base station to a target base station, as identified by measurement reports provided by that user equipment. The user equipment identifies the measured characteristics of signals received from a target base station.
Relocation during a substantially inactive state (such as cell_FACH) of user equipment typically does not require involvement of an RNC to allow the user equipment to relocate to a target base station.
As the configuration, operation and arrangement of network nodes such as base stations and user equipment within a wireless telecommunications network becomes increasingly complex, unexpected situations can occur which reduce the likelihood of a successful and efficient relocation occurring.
Accordingly, it is desired to provide an improved technique for facilitating relocation.